The primary goal of the Cellular Kinetics Section is to develop a better understanding of the kinetic behavior of normal and tumorous tissues and to use such information to design optimal forms of chemotherapy. Toward this end both animal studies and studies in patients have been undertaken. This year alterations in DNA synthesis induced by chemotherapy in normal and tumorous tissues have been studied after 5-FU, MeCCNU and 5-azacytidine. Nucleoside pool size alterations have been defined after 5-FU therapy in vivo. Kinetic studies in patients with ovarian cancer after methotrexate therapy and studies in patients with chronic myelogenous leukemia after 5-azacytidine have been carried out. Studies are presently underway studying alterations in DNA synthesis induced by Methotrexate in head and neck tumors. Flow microfluorometry studies of ascites tumor from patients with breast and ovarian tumors have been sequentially analyzed after treatment.